This invention relates to diagnostic circuits for computer controlled machine tools or the like. In the past, a diagnostic communication system has been designed which interlinks any one of a number of geographically separated, computer controlled machine tools with diagnostic and analysis equipment in a central diagnostic unit which is remote from the machine tools. This diagnostic communication system is described in U.S. Pat. No. 3,882,305, which was issued on May 6, 1975, for a "Diagnostic Communication System for Computer Controlled Machine Tools". In this system, the computer associated with any selected machine tool is connected with the diagnostic apparatus over a telephone line, and the machine tool is caused to execute a predetermined diagnostic routine in response to instructions transmitted to the machine tool computer from the diagnostic apparatus. The operating characteristics of the machine tool are monitored during the operation thereof and are communicated to the diagnostic apparatus, where they are compared with corresponding characteristics previously collected for the same machine tool, and with design limit parameters. Such comparisons enable an analyst at the remote diagnostic site to diagnose actual or incipient faults in the machine tool.
The above-described diagnostic communication system has one major shortcoming in that it is limited to monitoring machine tool characteristics which are expressed as digital signals and has no provision for monitoring analog signals, although there are analog signals in the machine tool which in some cases are more revealing in regard to faults than are the digital signals. Accordingly, the principal object of this invention is to provide a method and apparatus for transmitting analog signals from a computer controlled machine tool to an analog display device in a remote location and for displaying the analog signals to aid in the diagnosis of existing or incipient faults in the machine tool.
Other objects and advantages of the invention will be apparent from the description which follows.